🦋 express-openapi-validator

An OpenApi validator for ExpressJS that automatically validates API requests and responses using an OpenAPI 3 specification.

🦋express-openapi-validator is an unopinionated library that integrates with new and existing API applications. express-openapi-validator lets you write code the way you want; it does not impose any coding convention or project layout. Simply, install the validator onto your express app, point it to your OpenAPI 3 specification, then define and implement routes the way you prefer. See an example.

Features:

• ✔️ request validation
• ✔️ response validation (json only)
• 👮 security validation / custom security functions
• 👽 3rd party / custom formats / custom data serialization-deserialization
• 🧵 optionally auto-map OpenAPI endpoints to Express handler functions
• ✂️ $ref support; split specs over multiple files
• 🎈 file upload

NestJS Koa and Fastify now available! 🚀

Install

npm install express-openapi-validator

Usage

1. Require/import the openapi validator

const OpenApiValidator = require('express-openapi-validator');

or

import * as OpenApiValidator from 'express-openapi-validator';

2. Install the middleware

app.use(
  OpenApiValidator.middleware({
    apiSpec: './openapi.yaml',
    validateRequests: true, // (default)
    validateResponses: true, // false by default
  }),
);

3. Register an error handler

app.use((err, req, res, next) => {
  // format error
  res.status(err.status || 500).json({
    message: err.message,
    errors: err.errors,
  });
});

Important: Ensure express is configured with all relevant body parsers. Body parser middleware functions must be specified prior to any validated routes. See an example.

Upgrading from 3.x

In v4.x.x, the validator is installed as standard connect middleware using app.use(...) and/or router.use(...) (example). This differs from the v3.x.x the installation which required the install method(s). The install methods no longer exist in v4.

Usage (options)

See Advanced Usage options to:

• inline api specs as JSON.
• configure request/response validation options
• customize authentication with security validation handlers.
• use OpenAPI 3.0.x 3rd party and custom formats.
• tweak the file upload configuration.
• ignore routes
• and more...

Example Express API Server

The following demonstrates how to use express-openapi-validator to auto validate requests and responses. It also includes file upload!

See the complete source code and OpenAPI spec for the example below:

const express = require('express');
const path = require('path');
const http = require('http');
const app = express();

// 1. Import the express-openapi-validator library
const OpenApiValidator = require('express-openapi-validator');

// 2. Set up body parsers for the request body types you expect
//    Must be specified prior to endpoints in 5.
app.use(express.json());
app.use(express.text());
app.use(express.urlencoded({ extended: false }));

// 3. (optionally) Serve the OpenAPI spec
const spec = path.join(__dirname, 'api.yaml');
app.use('/spec', express.static(spec));

// 4. Install the OpenApiValidator onto your express app
app.use(
  OpenApiValidator.middleware({
    apiSpec: './api.yaml',
    validateResponses: true, // <-- to validate responses
  }),
);

// 5. Define routes using Express
app.get('/v1/pets', function (req, res, next) {
  res.json([
    { id: 1, type: 'cat', name: 'max' },
    { id: 2, type: 'cat', name: 'mini' },
  ]);
});

app.post('/v1/pets', function (req, res, next) {
  res.json({ name: 'sparky', type: 'dog' });
});

app.get('/v1/pets/:id', function (req, res, next) {
  res.json({ id: req.params.id, type: 'dog', name: 'sparky' });
});

// 5a. Define route(s) to upload file(s)
app.post('/v1/pets/:id/photos', function (req, res, next) {
  // files are found in req.files
  // non-file multipart params can be found as such: req.body['my-param']
  res.json({
    files_metadata: req.files.map((f) => ({
      originalname: f.originalname,
      encoding: f.encoding,
      mimetype: f.mimetype,
      // Buffer of file conents
      buffer: f.buffer,
    })),
  });
});

// 6. Create an Express error handler
app.use((err, req, res, next) => {
  // 7. Customize errors
  console.error(err); // dump error to console for debug
  res.status(err.status || 500).json({
    message: err.message,
    errors: err.errors,
  });
});

http.createServer(app).listen(3000);

Example Express API Server: with operationHandlers

Don't want to manually map your OpenAPI endpoints to Express handler functions? express-openapi-validator can do it for you, automatically!

Use express-openapi-validator's OpenAPI x-eov-operation-* vendor extensions. See a full example with source code and an OpenAPI spec

Here's the gist

• First, specify the operationHandlers option to set the base directory that contains your operation handler files.

app.use(
  OpenApiValidator.middleware({
    apiSpec,
    operationHandlers: path.join(__dirname),
  }),
);

• Next, use the x-eov-operation-id OpenAPI vendor extension or operationId to specify the id of operation handler to invoke.

/ping:
  get:
    # operationId: ping
    x-eov-operation-id: ping

• Next, use the x-eov-operation-handler OpenAPI vendor extension to specify a path (relative to operationHandlers) to the module that contains the handler for this operation.

/ping:
  get:
    x-eov-operation-id: ping
    x-eov-operation-handler: routes/ping # no .js or .ts extension

• Finally, create the express handler module e.g. routes/ping.js

module.exports = {
  // the express handler implementation for ping
  ping: (req, res) => res.status(200).send('pong'),
};

Note: A file may contain one or many handlers.

Below are some code snippets:

app.js

const express = require('express');
const path = require('path');
const bodyParser = require('body-parser');
const logger = require('morgan');
const http = require('http');
const OpenApiValidator = require('express-openapi-validator');

const port = 3000;
const app = express();
const apiSpec = path.join(__dirname, 'api.yaml');

// 1. Install bodyParsers for the request types your API will support
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.text());
app.use(bodyParser.json());

app.use(logger('dev'));

app.use('/spec', express.static(apiSpec));

//  2. Install the OpenApiValidator on your express app
app.use(
  OpenApiValidator.middleware({
    apiSpec,
    validateResponses: true, // default false
    // 3. Provide the base path to the operation handlers directory
    operationHandlers: path.join(__dirname), // default false
  }),
);

// 4. Woah sweet! With auto-wired operation handlers, I don't have to declare my routes!
//    See api.yaml for x-eov-* vendor extensions

// 5. Create a custom error handler
app.use((err, req, res, next) => {
  // format errors
  res.status(err.status || 500).json({
    message: err.message,
    errors: err.errors,
  });
});

http.createServer(app).listen(port);
console.log(`Listening on port ${port}`);

module.exports = app;

api.yaml

/ping:
  get:
    description: |
      ping then pong!
    # OpenAPI's operationId may be used to to specify the operation id
    operationId: ping
    # x-eov-operation-id may be used to specify the operation id
    # Used when operationId is omitted. Overrides operationId when both are specified
    x-eov-operation-id: ping
    # specifies the path to the operation handler.
    # the path is relative to the operationHandlers option
    # e.g. operations/base/path/routes/ping.js
    x-eov-operation-handler: routes/ping
    responses:
      '200':
        description: OK
        # ...

ping.js

module.exports = {
  // ping must match operationId or x-eov-operation-id above
  // note that x-eov-operation-id overrides operationId
  ping: (req, res) => res.status(200).send('pong'),
};

API Validation Response Examples

Validates a query parameter with a value constraint

curl -s http://localhost:3000/v1/pets/as |jq
{
  "message": "request.params.id should be integer",
  "errors": [
    {
      "path": ".params.id",
      "message": "should be integer",
      "errorCode": "type.openapi.validation"
    }
  ]
}

Validates a query parameter with a range constraint

 curl -s 'http://localhost:3000/v1/pets?limit=25' |jq
{
  "message": "request.query should have required property 'type', request.query.limit should be <= 20",
  "errors": [
    {
      "path": ".query.type",
      "message": "should have required property 'type'",
      "errorCode": "required.openapi.validation"
    },
    {
      "path": ".query.limit",
      "message": "should be <= 20",
      "errorCode": "maximum.openapi.validation"
    }
  ]
}

Validates securities e.g. API Key

 curl -s --request POST \
  --url http://localhost:3000/v1/pets \
  --data '{}' |jq
{
  "message": "'X-API-Key' header required",
  "errors": [
    {
      "path": "/v1/pets",
      "message": "'X-API-Key' header required"
    }
  ]
}

Providing the header passes OpenAPI validation.

Note: that your Express middleware or endpoint logic can then provide additional checks.

curl -XPOST http://localhost:3000/v1/pets \
  --header 'X-Api-Key: XXXXX' \
  --header 'content-type: application/json' \
  -d '{"name": "spot"}' | jq

{
  "id": 4,
  "name": "spot"
}

Validates content-type

curl -s --request POST \
  --url http://localhost:3000/v1/pets \
  --header 'content-type: application/xml' \
  --header 'x-api-key: XXXX' \
  --data '{
        "name": "test"
}' |jq
  "message": "unsupported media type application/xml",
  "errors": [
    {
      "path": "/v1/pets",
      "message": "unsupported media type application/xml"
    }
  ]
}

Validates a POST request body

curl -s --request POST \
  --url http://localhost:3000/v1/pets \
  --header 'content-type: application/json' \
  --header 'x-api-key: XXXX' \
  --data '{}'|jq
{
  "message": "request.body should have required property 'name'",
  "errors": [
    {
      "path": ".body.name",
      "message": "should have required property 'name'",
      "errorCode": "required.openapi.validation"
    }
  ]
}

File Upload (out of the box)

curl -XPOST http://localhost:3000/v1/pets/10/photos -F file=@app.js|jq
{
  "files_metadata": [
    {
      "originalname": "app.js",
      "encoding": "7bit",
      "mimetype": "application/octet-stream"
    }
  ]
}

Validates responses (optional)

Errors in response validation return 500, not of 400

/v1/pets/99 will return a response that does not match the spec

 curl -s 'http://localhost:3000/v1/pets/99' |jq
{
  "message": ".response should have required property 'name', .response should have required property 'id'",
  "errors": [
    {
      "path": ".response.name",
      "message": "should have required property 'name'",
      "errorCode": "required.openapi.validation"
    },
    {
      "path": ".response.id",
      "message": "should have required property 'id'",
      "errorCode": "required.openapi.validation"
    }
  ]
}

...and much more. Try it out!

Response status codes

express-openapi-validator returns the following error codes depending on the situation.

Request validation (validateRequests=true)

status	when
400 (bad request)	a validation error is encountered
401 (unauthorized)	a security / authentication errors is encountered e.g. missing api-key, Authorization header, etc
404 (not found)	a path is not found i.e. not declared in the API spec
405 (method not allowed)	a path is declared in the API spec, but a no schema is provided for the method

Response validation (validateResponses=true)

status	when
500 (internal server error)	any error is encountered by the validator

Advanced Usage

OpenApiValidator Middleware Options

express-openapi validator provides a good deal of flexibility via its options.

Options are provided via the options object. Options take the following form:

OpenApiValidator.middleware({
  apiSpec: './openapi.yaml',
  validateRequests: true,
  validateResponses: true,
  validateApiSpec: true,
  validateSecurity: {
    handlers: {
      ApiKeyAuth: (req, scopes, schema) => {
        throw { status: 401, message: 'sorry' }
      }
    }
  },
  validateFormats: 'fast',
  formats: [{
    name: 'my-custom-format',
    type: 'string' | 'number',
    validate: (value: any) => boolean,
  }],
  unknownFormats: ['phone-number', 'uuid'],
  serDes: [{
    OpenApiValidator.serdes.dateTime,
    OpenApiValidator.serdes.date,
    {
      format: 'mongo-objectid',
      deserialize: (s) => new ObjectID(s),
      serialize: (o) => o.toString(),
    },
  }],
  operationHandlers: false | 'operations/base/path' | { ... },
  ignorePaths: /.*\/pets$/,
  fileUploader: { ... } | true | false,
  $refParser: {
    mode: 'bundle'
  },
});

▪️ apiSpec (required)

Specifies the path to an OpenAPI 3 specification or a JSON object representing the OpenAPI 3 specification

apiSpec: './path/to/my-openapi-spec.yaml';

or

  apiSpec: {
  openapi: '3.0.1',
  info: {...},
  servers: [...],
  paths: {...},
  components: {
    responses: {...},
    schemas: {...}
  }
}

▪️ validateRequests (optional)

Determines whether the validator should validate requests.

• true (default) - validate requests.

• false - do not validate requests.

• { ... } - validate requests with options

  allowUnknownQueryParameters:

  • true - enables unknown/undeclared query parameters to pass validation
  • false - (default) fail validation if an unknown query parameter is present

  For example:

  validateRequests: {
    allowUnknownQueryParameters: true;
  }

  allowUnknownQueryParameters is set for the entire validator. It can be overwritten per-operation using a custom property x-allow-unknown-query-parameters.

  For example to allow unknown query parameters on ONLY a single endpoint:

  paths:
    /allow_unknown:
      get:
        x-allow-unknown-query-parameters: true
        parameters:
          - name: value
            in: query
            schema:
              type: string
        responses:
          200:
            description: success

  coerceTypes:

  Determines whether the validator will coerce the request body. Request query and path params, headers, cookies are coerced by default and this setting does not affect that.

  Options:

  • true - coerce scalar data types.
  • false - (default) do not coerce types. (more strict, safer)
  • "array" - in addition to coercions between scalar types, coerce scalar data to an array with one element and vice versa (as required by the schema).

  For example:

  validateRequests: {
    coerceTypes: true;
  }

  removeAdditional:

  Determines whether to keep or remove additional properties in request body or to fail validation if schema has additionalProperties set to false. For further details, refer to AJV documentation

  • false (default) - not to remove additional properties
  • "all" - all additional properties are removed, regardless of additionalProperties keyword in schema (and no validation is made for them).
  • true - only additional properties with additionalProperties keyword equal to false are removed.
  • "failing" - additional properties that fail request schema validation will be removed (where additionalProperties keyword is false or schema).

  For example:

  validateRequests: {
    removeAdditional: true;
  }

▪️ validateResponses (optional)

Determines whether the validator should validate responses. Also accepts response validation options.

• true - validate responses in 'strict' mode i.e. responses MUST match the schema.

• false (default) - do not validate responses

• { ... } - validate responses with options

  removeAdditional:

  • "failing" - additional properties that fail schema validation are automatically removed from the response.

  coerceTypes:

  • true - coerce scalar data types.
  • false - (default) do not coerce types. (almost always the desired behavior)
  • "array" - in addition to coercions between scalar types, coerce scalar data to an array with one element and vice versa (as required by the schema).

  For example:

  validateResponses: {
    removeAdditional: 'failing';
  }

  onError:

  A function that will be invoked on response validation error, instead of the default handling. Useful if you want to log an error or emit a metric, but don't want to actually fail the request. Receives the validation error and offending response body.

  For example:

  validateResponses: {
    onError: (error, body) => {
      console.log(`Response body fails validation: `, error);
      console.debug(body);
    }
  }
  

▪️ validateSecurity (optional)

Determines whether the validator should validate securities e.g. apikey, basic, oauth2, openid, etc

• true (default) - validate security

• false - do not validate security

• { ... } - validate security with handlers. See Security handlers doc.

  handlers:

  For example:

  validateSecurity: {
    handlers: {
      ApiKeyAuth: function(req, scopes, schema) {
        console.log('apikey handler throws custom error', scopes, schema);
        throw Error('my message');
      },
    }
  }

▪️ validateApiSpec (optional)

Determines whether the validator should validate the OpenAPI specification. Useful if you are certain that the api spec is syntactically correct and want to bypass this check.

Warning: Be certain your spec is valid. And be sure you know what you're doing! express-openapi-validator expects a valid spec. If incorrect, the validator will behave erratically and/or throw Javascript errors.

• true (default) - validate the OpenAPI specification.
• false - do not validate the OpenAPI specification.

▪️ formats (optional)

Defines a list of custom formats.

• [{ ... }] - array of custom format objects. Each object must have the following properties:
  • name: string (required) - the format name
  • validate: (v: any) => boolean (required) - the validation function
  • type: 'string' | 'number' (optional) - the format's type

e.g.

formats: [
  {
    name: 'my-three-digit-format',
    type: 'number',
    // validate returns true the number has 3 digits, false otherwise
    validate: (v) => /^\d{3}$/.test(v.toString()),
  },
  {
    name: 'my-three-letter-format',
    type: 'string',
    // validate returns true the string has 3 letters, false otherwise
    validate: (v) => /^[A-Za-z]{3}$/.test(v),
  },
];

Then use it in a spec e.g.

my_property:
  type: string
  format: my-three-letter-format'

▪️ validateFormats (optional)

Specifies the strictness of validation of string formats.

• "fast" (default) - only validate syntax, but not semantics. E.g. 2010-13-30T23:12:35Z will pass validation even though it contains month 13.
• "full" - validate both syntax and semantics. Illegal dates will not pass.
• false - do not validate formats at all.

▪️ unknownFormats (optional)

Defines how the validator should behave if an unknown or custom format is encountered.

• true (default) - When an unknown format is encountered, the validator will report a 400 error.

• [string] (recommended for unknown formats) - An array of unknown format names that will be ignored by the validator. This option can be used to allow usage of third party schemas with format(s), but still fail if another unknown format is used. e.g.

  unknownFormats: ['phone-number', 'uuid'];

• "ignore" - to log warning during schema compilation and always pass validation. This option is not recommended, as it allows to mistype format name and it won't be validated without any error message.

▪️ serDes (optional)

Defines custom serialization and deserialization behavior for schemas of type string that declare a format. By default, Date objects are serialized as string when a schema's type is string and format is date or date-time.

e.g.

// If `serDes` is not specified, the following behavior is default
serDes: [{
  OpenApiValidator.serdes.dateTime.serializer,
  OpenApiValidator.serdes.date.serializer,
}],

To create custom serializers and/or deserializers, define:

• format (required) - a custom 'unknown' format that triggers the serializer and/or deserializer
• deserialize (optional) - upon receiving a request, transform a string property to an object. Deserialization occurs after request schema validation.
• serialize (optional) - before sending a response, transform an object to string. Serialization occurs after response schema validation

e.g.

serDes: [{
   // installs dateTime serializer and deserializer
  OpenApiValidator.serdes.dateTime,
  // installs date serializer and deserializer
  OpenApiValidator.serdes.date,
  // custom serializer and deserializer for the custom format, mongo-objectid
  {
    format: 'mongo-objectid',
    deserialize: (s) => new ObjectID(s),
    serialize: (o) => o.toString(),
  }
}],

The mongo serializers will trigger on the following schema:

type: string
format: mongo-objectid

See mongo-serdes-js for additional (de)serializers including MongoDB ObjectID, UUID, ...

▪️ operationHandlers (optional)

Defines the base directory for operation handlers. This is used in conjunction with express-openapi-validator's OpenAPI vendor extensions, x-eov-operation-id, x-eov-operation-handler and OpenAPI's operationId. See example.

Additionally, if you want to change how modules are resolved e.g. use dot delimited operation ids e.g. path.to.module.myFunction, you may optionally add a custom resolver. See documentation and example

• string - the base directory containing operation handlers

• false - (default) disable auto wired operation handlers

• { ... } - specifies a base directory and optionally a custom resolver

  handlers:

  For example:

  operationHandlers: {
    basePath: __dirname,
    resolver: function (modulePath, route): express.RequestHandler {
      ///...
    }
  }

operationHandlers: 'operations/base/path'

Note that the x-eov-operation-handler OpenAPI vendor extension specifies a path relative to operationHandlers. Thus if operationHandlers is /handlers and an x-eov-operation-handler has path routes/ping, then the handler file /handlers/routes/ping.js (or ts) is used.

Complete example here

api.yaml

/ping:
  get:
    description: |
      ping then pong!
    # OpenAPI's operationId may be used to to specify the operation id
    operationId: ping
    # x-eov-operation-id may be used to specify the operation id
    # Used when operationId is omitted. Overrides operationId when both are specified
    x-eov-operation-id: ping
    # specifies the path to the operation handler.
    # the path is relative to the operationHandlers option
    # e.g. operations/base/path/routes/ping.js
    x-eov-operation-handler: routes/ping
    responses:
      '200':
        description: OK
        # ...

routes/ping.js

x-eov-operation-handler specifies the path to this handlers file, ping.js

x-eov-operation-id (or operationId) specifies operation handler's key e.g. ping

module.exports = {
  ping: (req, res) => res.status(200).send('pong'),
};

▪️ ignorePaths (optional)

Defines a regular expression or function that determines whether a path(s) should be ignored. If it's a regular expression, any path that matches the regular expression will be ignored by the validator. If it's a function, it will ignore any paths that returns a truthy value.

The following ignores any path that ends in /pets e.g. /v1/pets. As a regular expression:

ignorePaths: /.*\/pets$/

or as a function:

ignorePaths: (path) => path.endsWith('/pets')

▪️ fileUploader (optional)

Specifies the options to passthrough to multer. express-openapi-validator uses multer to handle file uploads. see multer opts

• true (default) - enables multer and provides simple file(s) upload capabilities

• false - disables file upload capability. Upload capabilities may be provided by the user

• {...} - multer options to be passed-through to multer. see multer opts for possible options

  e.g.

  fileUploader: {
    dest: 'uploads/';
  }

▪️ $refParser.mode (optional)

Determines how JSON schema references are resolved by the internal json-schema-ref-parser. Generally, the default mode, bundle is sufficient, however if you use escape characters in $refs, dereference is necessary.

• bundle (default) - Bundles all referenced files/URLs into a single schema that only has internal $ref pointers. This eliminates the risk of circular references, but does not handle escaped characters in $refs.
• dereference - Dereferences all $ref pointers in the JSON Schema, replacing each reference with its resolved value. Introduces risk of circular $refs. Handles escape characters in $refs)

See this issue for more information.

e.g.

$refParser: {
  mode: 'bundle';
}

▪️ coerceTypes (optional) - deprecated

Determines whether the validator should coerce value types to match the those defined in the OpenAPI spec. This option applies only to path params, query strings, headers, and cookies. It is highly unlikely that you will want to disable this. As such this option is deprecated and will be removed in the next major version

• true (default) - coerce scalar data types.
• "array" - in addition to coercions between scalar types, coerce scalar data to an array with one element and vice versa (as required by the schema).

The Base URL

The validator will only validate requests, securities, and responses that are under the server's base URL.

This is useful for those times when the API and frontend are being served by the same application. (More detail about the base URL.)

servers:
  - url: https://api.example.com/v1

The validation applies to all paths defined under this base URL. Routes in your app that are _not_se URL—such as pages—will not be validated.

URL	Validated?
https://api.example.com/v1/users	✅
https://api.example.com/index.html	no; not under the base URL

In some cases, it may be necessary to skip validation for paths under the base url. To do this, use the ignorePaths option.

Security handlers

Note: security handlers are an optional component. security handlers provide a convenience, whereby the request, declared scopes, and the security schema itself are provided as parameters to each security handlers callback that you define. The code you write in each callback can then perform authentication and authorization checks. Note that the same can be achieved using standard Express middleware. The difference is that security handlers provide you the OpenAPI schema data described in your specification_. Ultimately, this means, you don't have to duplicate that information in your code.

All in all, security handlers are purely optional and are provided as a convenience.

Security handlers specify a set of custom security handlers to be used to validate security i.e. authentication and authorization. If a security handlers object is specified, a handler must be defined for all securities. If security `handlers are not specified, a default handler is always used. The default handler will validate against the OpenAPI spec, then call the next middleware.

If security handlers are specified, the validator will validate against the OpenAPI spec, then call the security handler providing it the Express request, the security scopes, and the security schema object.

• security handlers is an object that maps security keys to security handler functions. Each security key must correspond to securityScheme name. The validateSecurity.handlers object signature is as follows:

  {
    validateSecurity: {
      handlers: {
        [securityKey]: function(
          req: Express.Request,
          scopes: string[],
          schema: SecuritySchemeObject
        ): void,
      }
    }
  }

  SecuritySchemeObject

  For example:

  validateSecurity: {
    handlers: {
      ApiKeyAuth: function(req, scopes, schema) {
        console.log('apikey handler throws custom error', scopes, schema);
        throw Error('my message');
      },
    }
  }

The express-openapi-validator performs a basic validation pass prior to delegating to security handlers. If basic validation passes, security handler function(s) are invoked.

In order to signal an auth failure, the security handler function must either:

1. throw { status: 403, message: 'forbidden' }
2. throw Error('optional message')
3. return false
4. return a promise which resolves to false e.g Promise.resolve(false)
5. return a promise rejection e.g.
   • Promise.reject({ status: 401, message: 'yikes' });
   • Promise.reject(Error('optional 'message')
   • Promise.reject(false)

Note: error status 401 is returned, unless option i. above is used

Some examples:

validateSecurity: {
  handlers: {
    ApiKeyAuth: (req, scopes, schema) => {
      throw Error('my message');
    },
    OpenID: async (req, scopes, schema) => {
      throw { status: 403, message: 'forbidden' }
    },
    BasicAuth: (req, scopes, schema) => {
      return Promise.resolve(false);
    },
    ...
  }
}

In order to grant authz, the handler function must either:

• return true
• return a promise which resolves to true

Some examples

validateSecurity: {
  handlers: {
    ApiKeyAuth: (req, scopes, schema) => {
      return true;
    },
    BearerAuth: async (req, scopes, schema) => {
      return true;
    },
    ...
  }
}

Each security handlers' securityKey must match a components/securitySchemes property

components:
  securitySchemes:
    ApiKeyAuth: # <-- Note this name must be used as the name handler function property
      type: apiKey
      in: header
      name: X-API-Key

See OpenAPI 3 authentication for securityScheme and security documentation See examples from unit tests

Example: Multiple Validators and API specs

It may be useful to serve multiple APIs with separate specs via single service. An example might be an API that serves both v1 and v2 from the same service. The sample code below shows how one might accomplish this.

See complete example

const express = require('express');
const path = require('path');
const bodyParser = require('body-parser');
const http = require('http');
const OpenApiValidator = require('express-openapi-validator');

app = express();
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.text());
app.use(bodyParser.json());

const versions = [1, 2];

for (const v of versions) {
  const apiSpec = path.join(__dirname, `api.v${v}.yaml`);
  app.use(
    OpenApiValidator.middleware({
      apiSpec,
    }),
  );

  routes(app, v);
}

http.createServer(app).listen(3000);
console.log('Listening on port 3000');

function routes(app, v) {
  if (v === 1) routesV1(app);
  if (v === 2) routesV2(app);
}

function routesV1(app) {
  const v = '/v1';
  app.post(`${v}/pets`, (req, res, next) => {
    res.json({ ...req.body });
  });
  app.get(`${v}/pets`, (req, res, next) => {
    res.json([
      {
        id: 1,
        name: 'happy',
        type: 'cat',
      },
    ]);
  });

  app.use((err, req, res, next) => {
    // format error
    res.status(err.status || 500).json({
      message: err.message,
      errors: err.errors,
    });
  });
}

function routesV2(app) {
  const v = '/v2';
  app.get(`${v}/pets`, (req, res, next) => {
    res.json([
      {
        pet_id: 1,
        pet_name: 'happy',
        pet_type: 'kitty',
      },
    ]);
  });
  app.post(`${v}/pets`, (req, res, next) => {
    res.json({ ...req.body });
  });

  app.use((err, req, res, next) => {
    // format error
    res.status(err.status || 500).json({
      message: err.message,
      errors: err.errors,
    });
  });
}

module.exports = app;

FAQ

Q: How do I match paths, like those described in RFC-6570?

A: OpenAPI 3.0 does not support RFC-6570. That said, we provide a minimalistic mechanism that conforms syntactically to OpenAPI 3 and accomplishes a common use case. For example, matching file paths and storing the matched path in req.params

Using the following OpenAPI 3.x definition

/files/{path}*:
  get:
    parameters:
      - name: path
        in: path
        required: true
        schema:
          type: string

With the following Express route definition

  app.get(`/files/:path(*)`, (req, res) => { /* do stuff */ }`

A path like /files/some/long/path will pass validation. The Express req.params.path property will hold the value some/long/path.

Q: Can I use discriminators with oneOf and anyOf?

A: Currently, there is support for top level discriminators. See top-level discriminator example

Q: What happened to the securityHandlers property?

A: In v3, securityHandlers have been replaced by validateSecurity.handlers. To use v3 security handlers, move your existing security handlers to the new property. No other change is required. Note that the v2 securityHandlers property is supported in v3, but deprecated

Q: What happened to the multerOpts property?

A: In v3, multerOpts have been replaced by fileUploader. In order to use the v3 fileUploader, move your multer options to fileUploader No other change is required. Note that the v2 multerOpts property is supported in v3, but deprecated

Q: I can disallow unknown query parameters with allowUnknownQueryParameters: false. How can disallow unknown body parameters?

A: Add additionalProperties: false when describing e.g a requestBody to ensure that additional properties are not allowed. For example:

Pet:
additionalProperties: false
required:
  - name
properties:
  name:
    type: string
  type:
    type: string

Q: Can I use express-openapi-validator with swagger-ui-express?

A: Yes. Be sure to use the swagger-ui-express serve middleware prior to installing OpenApiValidator. This will ensure that swagger-ui-express is able to fully prepare the spec before before OpenApiValidator attempts to use it. For example:

const swaggerUi = require('swagger-ui-express')
const OpenApiValidator = require('express-openapi-validator')

...

app.use('/', swaggerUi.serve, swaggerUi.setup(documentation))

app.use(OpenApiValidator.middleware({
  apiSpec, // api spec JSON object
  //... other options
  }
}))

Q: I have a handler function defined on an express.Router. If i call req.params each param value has type string. If i define same handler function on an express.Application, each value in req.params is already coerced to the type declare in my spec. Why not coerce theseF values on an express.Router?

A: First, it's important to note that this behavior does not impact validation. The validator will validate against the type defined in your spec.

In order to modify the req.params, express requires that a param handler be registered e.g. app.param(...) or router.param(...). Since app is available to middleware functions, the validator registers an app.param handler to coerce and modify the values of req.params to their declared types. Unfortunately, express does not provide a means to determine the current router from a middleware function, hence the validator is unable to register the same param handler on an express router. Ultimately, this means if your handler function is defined on app, the values of req.params will be coerced to their declared types. If your handler function is declare on an express.Router, the values of req.params values will be of type string (You must coerce them e.g. parseInt(req.params.id)).

Related Projects

• koa-openapi-validator
• fastify-openapi-validator

_Note: koa and fastify does not (yet) support response validation or operation handlers

Contributors ✨

Contributions welcome! Here's how to contribute.

Thanks goes to these wonderful people (emoji key):

Carmine DiMascio 💻 ⚠️ 🚇	Sheldhur Mornor 💻 ⚠️	Andrey Trebler 💻 ⚠️	richdouglasevans 📖	Miran Setinc 💻	Frank Calise 💻	Gonen Dukas 🤔 ⚠️
Sven Eliasson 💻 ⚠️	Spencer Brown 💻 ⚠️	José Neves 💻	mk811 💻 ⚠️	HugoMario 💻 ⚠️	Rowan Cockett 💻	Jacques Yakoub 💻
ckeboss 💻 ⚠️	JacobLey 💻 ⚠️	Dmitriy Voeykov 💻 ⚠️	GARAMKIM 💻 🤔	Mathias Scherer 💻	Mirek 💻	Florian Beutel 💻
jakubskopal 💻 ⚠️ 📖	Jordan Dobrev ⚠️ 💻	Enrico Fabris 💻	Dustin Wheeler 💻 📖 ⚠️	Thomas Carmichael 📖	Jakesterwars 📖	xtrycatchx 💻
Lee Dong Joo 📖	Dmitry Chekanov 💻 ⚠️	Redhart Azul 💻	Joost Diepenmaat 💻 ⚠️	Dom Parfitt 💻 ⚠️	xg1990 💻	ownagedj 💻 ⚠️
David Garner 💻	Balazs Soltesz 💻 ⚠️	Christiaan Nieuwlaat 💻	Ilya 💻 ⚠️	Yuliya Bagriy 💻 ⚠️	Kristjan Siimson 💻 ⚠️	Guillaume 💻 ⚠️
Volodymyr Kolesnykov 💻 ⚠️	Pierre Le Roux 💻 ⚠️ 🤔	Electro Type 🤔	Aaron Luman 💻 ⚠️

This project follows the all-contributors specification. Contributions of any kind welcome!

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License

MIT